After removing just a few layers of onion you realize that the core of Endless Space is ... empty. A boring void.
The good
UI! The biggest selling point of this game is the UI which on one hand look clean and extremely polished, while on the other it's easy to understand and use. A real pleasure.
The bad
Battles are pretty ... and that's it. During the first few fights you are hard pressed of choosing the proper cards. Later you just use one tactic. In the end you understand that it really doesn't make such a difference and you just auto-resolve not to waste time watching the same battle scenes.
The ugly
ES is set in space. Unfortunately the space doesn't seem very 'spacish'. It's empty. It's shallow, as the game itself.
80% of techs is just bit better this or that - not many of them truly provide you with unique advantage. The map/space itself is dull. No random events, lost civilizations, independent minor races, anomalies - nothing! AI adds to this insult by not being very smart.
The bottom line
ES is nice little polished game that needs more developers' attention so that it doesn't feel as a mixture of nothingness and similar features.